I removed the radio block off plate & made up a plate to mount my Garmin in. The speedo function is accurate and I use the Eco Route feature to track fuel use and MPG.
Visability in bright sun is usable, not as good as the OEM speedo but passable.
Pic
Pic

1949 Chevy 1/2-Ton 3100
1949 GMC 1/2-ton 100
In the Stovebolt Gallery
More pix on Photobucket
Video of the 216 running
Video of a Winter Cruise